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	$44.76	5.498%	$47.2209	$47.22	$47.20	$47.20
Purchase #2	$226.67	9.374%	$247.918	$247.92	$247.90	$247.90
Purchase #3	$59.46	9.163%	$64.9083	$64.91	$64.90	$64.90
Purchase #4	$233.51	13.222%	$264.3847	$264.38	$264.40	$264.40
Purchase #5	$233.71	13.496%	$265.2515	$265.25	$265.25	$265.30
Purchase #6	$213.95	6.348%	$227.5315	$227.53	$227.55	$227.50
Purchase #7	$37.54	13.316%	$42.5388	$42.54	$42.55	$42.50
7 purchase totals =	$1,049.60		$1,159.7537	$1,159.75	$1,159.75	$1,159.70