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	$136.74	11.253%	$152.1274	$152.13	$152.15	$152.10
Purchase #2	$147.33	13.626%	$167.4052	$167.41	$167.40	$167.40
Purchase #3	$89.61	7.434%	$96.2716	$96.27	$96.25	$96.30
Purchase #4	$157.94	5.326%	$166.3519	$166.35	$166.35	$166.40
Purchase #5	$41.72	12.221%	$46.8186	$46.82	$46.80	$46.80
Purchase #6	$194.51	6.532%	$207.2154	$207.22	$207.20	$207.20
Purchase #7	$84.95	3.261%	$87.7202	$87.72	$87.70	$87.70
7 purchase totals =	$852.80		$923.9103	$923.92	$923.85	$923.90