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	$167.73	7.854%	$180.9035	$180.90	$180.90	$180.90
Purchase #2	$171.74	7.313%	$184.2993	$184.30	$184.30	$184.30
Purchase #3	$78.89	4.324%	$82.3012	$82.30	$82.30	$82.30
Purchase #4	$73.58	4.701%	$77.039	$77.04	$77.05	$77.00
Purchase #5	$54.26	3.214%	$56.0039	$56.00	$56.00	$56.00
Purchase #6	$26.57	8.814%	$28.9119	$28.91	$28.90	$28.90
Purchase #7	$82.65	7.686%	$89.0025	$89.00	$89.00	$89.00
7 purchase totals =	$655.42		$698.4613	$698.45	$698.45	$698.40