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	$92.38	8.123%	$99.884	$99.88	$99.90	$99.90
Purchase #2	$99.84	5.806%	$105.6367	$105.64	$105.65	$105.60
Purchase #3	$178.87	8.673%	$194.3834	$194.38	$194.40	$194.40
Purchase #4	$183.50	6.870%	$196.1065	$196.11	$196.10	$196.10
Purchase #5	$179.34	7.645%	$193.0505	$193.05	$193.05	$193.10
Purchase #6	$250.92	6.705%	$267.7442	$267.74	$267.75	$267.70
Purchase #7	$76.91	5.870%	$81.4246	$81.42	$81.40	$81.40
7 purchase totals =	$1,061.76		$1,138.2299	$1,138.22	$1,138.25	$1,138.20