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	$236.69	11.851%	$264.7401	$264.74	$264.75	$264.70
Purchase #2	$115.96	13.602%	$131.7329	$131.73	$131.75	$131.70
Purchase #3	$59.91	3.413%	$61.9547	$61.95	$61.95	$62.00
Purchase #4	$125.81	6.601%	$134.1147	$134.11	$134.10	$134.10
Purchase #5	$125.41	13.817%	$142.7379	$142.74	$142.75	$142.70
Purchase #6	$150.56	7.715%	$162.1757	$162.18	$162.20	$162.20
Purchase #7	$206.45	13.225%	$233.753	$233.75	$233.75	$233.80
7 purchase totals =	$1,020.79		$1,131.2090	$1,131.20	$1,131.25	$1,131.20