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	$110.89	4.561%	$115.9477	$115.95	$115.95	$115.90
Purchase #2	$197.73	8.848%	$215.2252	$215.23	$215.25	$215.20
Purchase #3	$34.91	4.610%	$36.5194	$36.52	$36.50	$36.50
Purchase #4	$241.53	9.399%	$264.2314	$264.23	$264.25	$264.20
Purchase #5	$210.46	5.404%	$221.8333	$221.83	$221.85	$221.80
Purchase #6	$123.86	6.505%	$131.9171	$131.92	$131.90	$131.90
Purchase #7	$187.66	9.441%	$205.377	$205.38	$205.40	$205.40
7 purchase totals =	$1,107.04		$1,191.0511	$1,191.06	$1,191.10	$1,190.90