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	$119.53	5.340%	$125.9129	$125.91	$125.90	$125.90
Purchase #2	$183.91	6.645%	$196.1308	$196.13	$196.15	$196.10
Purchase #3	$119.76	4.254%	$124.8546	$124.85	$124.85	$124.90
Purchase #4	$41.97	7.604%	$45.1614	$45.16	$45.15	$45.20
Purchase #5	$103.47	5.640%	$109.3057	$109.31	$109.30	$109.30
Purchase #6	$114.51	5.394%	$120.6867	$120.69	$120.70	$120.70
Purchase #7	$46.57	12.410%	$52.3493	$52.35	$52.35	$52.30
7 purchase totals =	$729.72		$774.4014	$774.40	$774.40	$774.40