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	$167.41	12.597%	$188.4986	$188.50	$188.50	$188.50
Purchase #2	$37.75	4.705%	$39.5261	$39.53	$39.55	$39.50
Purchase #3	$165.86	4.209%	$172.841	$172.84	$172.85	$172.80
Purchase #4	$174.95	12.549%	$196.9045	$196.90	$196.90	$196.90
Purchase #5	$209.39	11.234%	$232.9129	$232.91	$232.90	$232.90
Purchase #6	$242.46	4.513%	$253.4022	$253.40	$253.40	$253.40
Purchase #7	$16.54	9.722%	$18.148	$18.15	$18.15	$18.10
7 purchase totals =	$1,014.36		$1,102.2333	$1,102.23	$1,102.25	$1,102.10