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	$250.65	12.472%	$281.9111	$281.91	$281.90	$281.90
Purchase #2	$75.51	3.607%	$78.2336	$78.23	$78.25	$78.20
Purchase #3	$195.89	7.274%	$210.139	$210.14	$210.15	$210.10
Purchase #4	$219.98	6.869%	$235.0904	$235.09	$235.10	$235.10
Purchase #5	$45.63	3.797%	$47.3626	$47.36	$47.35	$47.40
Purchase #6	$222.83	11.199%	$247.7847	$247.78	$247.80	$247.80
Purchase #7	$99.37	3.738%	$103.0845	$103.08	$103.10	$103.10
7 purchase totals =	$1,109.86		$1,203.6059	$1,203.59	$1,203.65	$1,203.60