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	$165.28	13.439%	$187.492	$187.49	$187.50	$187.50
Purchase #2	$191.89	11.668%	$214.2797	$214.28	$214.30	$214.30
Purchase #3	$161.38	3.570%	$167.1413	$167.14	$167.15	$167.10
Purchase #4	$98.64	10.805%	$109.2981	$109.30	$109.30	$109.30
Purchase #5	$243.98	4.195%	$254.215	$254.22	$254.20	$254.20
Purchase #6	$116.54	13.497%	$132.2694	$132.27	$132.25	$132.30
Purchase #7	$219.39	7.494%	$235.8311	$235.83	$235.85	$235.80
7 purchase totals =	$1,197.10		$1,300.5266	$1,300.53	$1,300.55	$1,300.50