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	$39.83	11.506%	$44.4128	$44.41	$44.40	$44.40
Purchase #2	$245.37	4.119%	$255.4768	$255.48	$255.50	$255.50
Purchase #3	$34.69	4.356%	$36.2011	$36.20	$36.20	$36.20
Purchase #4	$80.51	9.632%	$88.2647	$88.26	$88.25	$88.30
Purchase #5	$40.74	6.356%	$43.3294	$43.33	$43.35	$43.30
Purchase #6	$47.56	7.821%	$51.2797	$51.28	$51.30	$51.30
Purchase #7	$76.65	7.847%	$82.6647	$82.66	$82.65	$82.70
7 purchase totals =	$565.35		$601.6292	$601.62	$601.65	$601.70