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	$144.47	9.457%	$158.1325	$158.13	$158.15	$158.10
Purchase #2	$37.91	5.784%	$40.1027	$40.10	$40.10	$40.10
Purchase #3	$162.49	7.360%	$174.4493	$174.45	$174.45	$174.40
Purchase #4	$129.31	11.593%	$144.3009	$144.30	$144.30	$144.30
Purchase #5	$209.49	6.821%	$223.7793	$223.78	$223.80	$223.80
Purchase #6	$213.70	8.127%	$231.0674	$231.07	$231.05	$231.10
Purchase #7	$147.78	4.751%	$154.801	$154.80	$154.80	$154.80
7 purchase totals =	$1,045.15		$1,126.6331	$1,126.63	$1,126.65	$1,126.60