Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$91.68	10.440%	$101.2514	$101.25	$101.25	$101.30
Purchase #2	$219.94	10.636%	$243.3328	$243.33	$243.35	$243.30
Purchase #3	$233.78	12.816%	$263.7412	$263.74	$263.75	$263.70
Purchase #4	$202.26	10.329%	$223.1514	$223.15	$223.15	$223.20
Purchase #5	$130.83	10.302%	$144.3081	$144.31	$144.30	$144.30
Purchase #6	$89.99	11.188%	$100.0581	$100.06	$100.05	$100.10
Purchase #7	$152.73	3.852%	$158.6132	$158.61	$158.60	$158.60
7 purchase totals =	$1,121.21		$1,234.4562	$1,234.45	$1,234.45	$1,234.50