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	$49.86	12.111%	$55.8985	$55.90	$55.90	$55.90
Purchase #2	$100.46	13.581%	$114.1035	$114.10	$114.10	$114.10
Purchase #3	$166.78	9.670%	$182.9076	$182.91	$182.90	$182.90
Purchase #4	$27.85	3.316%	$28.7735	$28.77	$28.75	$28.80
Purchase #5	$155.58	3.379%	$160.837	$160.84	$160.85	$160.80
Purchase #6	$83.35	9.803%	$91.5208	$91.52	$91.50	$91.50
Purchase #7	$105.32	12.346%	$118.3228	$118.32	$118.30	$118.30
7 purchase totals =	$689.20		$752.3637	$752.36	$752.30	$752.30