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	$99.58	7.363%	$106.9121	$106.91	$106.90	$106.90
Purchase #2	$64.35	10.811%	$71.3069	$71.31	$71.30	$71.30
Purchase #3	$61.69	4.323%	$64.3569	$64.36	$64.35	$64.40
Purchase #4	$43.88	12.719%	$49.4611	$49.46	$49.45	$49.50
Purchase #5	$71.50	7.495%	$76.8589	$76.86	$76.85	$76.90
Purchase #6	$152.99	12.611%	$172.2836	$172.28	$172.30	$172.30
Purchase #7	$172.29	11.104%	$191.4211	$191.42	$191.40	$191.40
7 purchase totals =	$666.28		$732.6006	$732.60	$732.55	$732.70