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	$146.70	5.194%	$154.3196	$154.32	$154.30	$154.30
Purchase #2	$100.59	5.222%	$105.8428	$105.84	$105.85	$105.80
Purchase #3	$96.30	3.518%	$99.6878	$99.69	$99.70	$99.70
Purchase #4	$71.70	9.533%	$78.5352	$78.54	$78.55	$78.50
Purchase #5	$150.92	10.459%	$166.7047	$166.70	$166.70	$166.70
Purchase #6	$188.31	7.799%	$202.9963	$203.00	$203.00	$203.00
Purchase #7	$168.42	6.368%	$179.145	$179.15	$179.15	$179.10
7 purchase totals =	$922.94		$987.2314	$987.24	$987.25	$987.10