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	$43.67	8.487%	$47.3763	$47.38	$47.40	$47.40
Purchase #2	$58.60	5.347%	$61.7333	$61.73	$61.75	$61.70
Purchase #3	$31.43	6.584%	$33.4994	$33.50	$33.50	$33.50
Purchase #4	$177.88	10.319%	$196.2354	$196.24	$196.25	$196.20
Purchase #5	$180.36	4.740%	$188.9091	$188.91	$188.90	$188.90
Purchase #6	$123.40	8.106%	$133.4028	$133.40	$133.40	$133.40
Purchase #7	$174.54	11.303%	$194.2683	$194.27	$194.25	$194.30
7 purchase totals =	$789.88		$855.4246	$855.43	$855.45	$855.40