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	$120.33	11.632%	$134.3268	$134.33	$134.35	$134.30
Purchase #2	$99.98	11.504%	$111.4817	$111.48	$111.50	$111.50
Purchase #3	$61.53	4.201%	$64.1149	$64.11	$64.10	$64.10
Purchase #4	$168.83	11.755%	$188.676	$188.68	$188.70	$188.70
Purchase #5	$175.96	13.233%	$199.2448	$199.24	$199.25	$199.20
Purchase #6	$109.42	7.188%	$117.2851	$117.29	$117.30	$117.30
Purchase #7	$180.36	9.806%	$198.0461	$198.05	$198.05	$198.00
7 purchase totals =	$916.41		$1,013.1754	$1,013.18	$1,013.25	$1,013.10