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	$55.36	10.691%	$61.2785	$61.28	$61.30	$61.30
Purchase #2	$175.44	6.662%	$187.1278	$187.13	$187.15	$187.10
Purchase #3	$197.41	12.862%	$222.8009	$222.80	$222.80	$222.80
Purchase #4	$196.44	13.164%	$222.2994	$222.30	$222.30	$222.30
Purchase #5	$183.34	9.715%	$201.1515	$201.15	$201.15	$201.20
Purchase #6	$185.30	13.740%	$210.7602	$210.76	$210.75	$210.80
Purchase #7	$37.51	11.524%	$41.8327	$41.83	$41.85	$41.80
7 purchase totals =	$1,030.80		$1,147.2510	$1,147.25	$1,147.30	$1,147.30