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	$189.25	11.130%	$210.3135	$210.31	$210.30	$210.30
Purchase #2	$18.52	8.682%	$20.1279	$20.13	$20.15	$20.10
Purchase #3	$19.59	8.171%	$21.1907	$21.19	$21.20	$21.20
Purchase #4	$96.42	7.162%	$103.3256	$103.33	$103.35	$103.30
Purchase #5	$131.30	12.230%	$147.358	$147.36	$147.35	$147.40
Purchase #6	$218.64	11.575%	$243.9476	$243.95	$243.95	$243.90
Purchase #7	$248.31	4.108%	$258.5106	$258.51	$258.50	$258.50
7 purchase totals =	$922.03		$1,004.7739	$1,004.78	$1,004.80	$1,004.70