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	$73.58	6.201%	$78.1427	$78.14	$78.15	$78.10
Purchase #2	$224.55	6.224%	$238.526	$238.53	$238.55	$238.50
Purchase #3	$118.54	6.144%	$125.8231	$125.82	$125.80	$125.80
Purchase #4	$91.52	13.832%	$104.179	$104.18	$104.20	$104.20
Purchase #5	$184.46	7.245%	$197.8241	$197.82	$197.80	$197.80
Purchase #6	$45.37	6.121%	$48.1471	$48.15	$48.15	$48.10
Purchase #7	$240.26	6.415%	$255.6727	$255.67	$255.65	$255.70
7 purchase totals =	$978.28		$1,048.3147	$1,048.31	$1,048.30	$1,048.20