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	$200.73	11.148%	$223.1074	$223.11	$223.10	$223.10
Purchase #2	$150.38	11.597%	$167.8196	$167.82	$167.80	$167.80
Purchase #3	$27.78	4.812%	$29.1168	$29.12	$29.10	$29.10
Purchase #4	$145.58	9.273%	$159.0796	$159.08	$159.10	$159.10
Purchase #5	$87.74	3.306%	$90.6407	$90.64	$90.65	$90.60
Purchase #6	$39.31	10.754%	$43.5374	$43.54	$43.55	$43.50
Purchase #7	$127.77	4.810%	$133.9157	$133.92	$133.90	$133.90
7 purchase totals =	$779.29		$847.2172	$847.23	$847.20	$847.10