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	$101.56	9.382%	$111.0884	$111.09	$111.10	$111.10
Purchase #2	$139.76	9.131%	$152.5215	$152.52	$152.50	$152.50
Purchase #3	$154.47	8.363%	$167.3883	$167.39	$167.40	$167.40
Purchase #4	$47.41	5.649%	$50.0882	$50.09	$50.10	$50.10
Purchase #5	$94.84	10.253%	$104.5639	$104.56	$104.55	$104.60
Purchase #6	$112.31	6.163%	$119.2317	$119.23	$119.25	$119.20
Purchase #7	$81.91	6.561%	$87.2841	$87.28	$87.30	$87.30
7 purchase totals =	$732.26		$792.1661	$792.16	$792.20	$792.20