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	$142.53	9.597%	$156.2086	$156.21	$156.20	$156.20
Purchase #2	$233.68	12.616%	$263.1611	$263.16	$263.15	$263.20
Purchase #3	$12.60	13.809%	$14.3399	$14.34	$14.35	$14.30
Purchase #4	$72.27	8.458%	$78.3826	$78.38	$78.40	$78.40
Purchase #5	$146.80	3.539%	$151.9953	$152.00	$152.00	$152.00
Purchase #6	$167.98	4.476%	$175.4988	$175.50	$175.50	$175.50
Purchase #7	$194.79	8.156%	$210.6771	$210.68	$210.70	$210.70
7 purchase totals =	$970.65		$1,050.2634	$1,050.27	$1,050.30	$1,050.30