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	$51.55	12.413%	$57.9489	$57.95	$57.95	$57.90
Purchase #2	$93.35	7.655%	$100.4959	$100.50	$100.50	$100.50
Purchase #3	$170.28	11.179%	$189.3156	$189.32	$189.30	$189.30
Purchase #4	$49.91	3.693%	$51.7532	$51.75	$51.75	$51.80
Purchase #5	$231.85	11.674%	$258.9162	$258.92	$258.90	$258.90
Purchase #6	$41.86	3.132%	$43.1711	$43.17	$43.15	$43.20
Purchase #7	$98.82	9.592%	$108.2988	$108.30	$108.30	$108.30
7 purchase totals =	$737.62		$809.8997	$809.91	$809.85	$809.90