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	$156.44	3.788%	$162.3659	$162.37	$162.35	$162.40
Purchase #2	$133.31	13.171%	$150.8683	$150.87	$150.85	$150.90
Purchase #3	$222.50	7.714%	$239.6637	$239.66	$239.65	$239.70
Purchase #4	$45.46	6.438%	$48.3867	$48.39	$48.40	$48.40
Purchase #5	$238.46	3.717%	$247.3236	$247.32	$247.30	$247.30
Purchase #6	$142.77	6.142%	$151.5389	$151.54	$151.55	$151.50
Purchase #7	$174.65	3.258%	$180.3401	$180.34	$180.35	$180.30
7 purchase totals =	$1,113.59		$1,180.4872	$1,180.49	$1,180.45	$1,180.50