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	$151.76	4.538%	$158.6469	$158.65	$158.65	$158.60
Purchase #2	$122.49	3.501%	$126.7784	$126.78	$126.80	$126.80
Purchase #3	$24.39	13.318%	$27.6383	$27.64	$27.65	$27.60
Purchase #4	$182.63	6.525%	$194.5466	$194.55	$194.55	$194.50
Purchase #5	$232.89	4.409%	$243.1581	$243.16	$243.15	$243.20
Purchase #6	$78.29	3.816%	$81.2775	$81.28	$81.30	$81.30
Purchase #7	$79.77	3.407%	$82.4878	$82.49	$82.50	$82.50
7 purchase totals =	$872.22		$914.5336	$914.55	$914.60	$914.50