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	$118.42	9.518%	$129.6912	$129.69	$129.70	$129.70
Purchase #2	$165.36	4.339%	$172.535	$172.54	$172.55	$172.50
Purchase #3	$88.88	9.247%	$97.0987	$97.10	$97.10	$97.10
Purchase #4	$192.41	3.369%	$198.8923	$198.89	$198.90	$198.90
Purchase #5	$47.39	12.561%	$53.3427	$53.34	$53.35	$53.30
Purchase #6	$131.82	7.375%	$141.5417	$141.54	$141.55	$141.50
Purchase #7	$85.55	6.643%	$91.2331	$91.23	$91.25	$91.20
7 purchase totals =	$829.83		$884.3347	$884.33	$884.40	$884.20