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	$72.76	13.426%	$82.5288	$82.53	$82.55	$82.50
Purchase #2	$64.96	11.275%	$72.2842	$72.28	$72.30	$72.30
Purchase #3	$142.82	4.418%	$149.1298	$149.13	$149.15	$149.10
Purchase #4	$59.99	4.233%	$62.5294	$62.53	$62.55	$62.50
Purchase #5	$179.90	7.422%	$193.2522	$193.25	$193.25	$193.30
Purchase #6	$246.33	3.209%	$254.2347	$254.23	$254.25	$254.20
Purchase #7	$29.78	13.258%	$33.7282	$33.73	$33.75	$33.70
7 purchase totals =	$796.54		$847.6873	$847.68	$847.80	$847.60