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	$173.29	3.318%	$179.0398	$179.04	$179.05	$179.00
Purchase #2	$31.77	13.851%	$36.1705	$36.17	$36.15	$36.20
Purchase #3	$43.59	4.173%	$45.409	$45.41	$45.40	$45.40
Purchase #4	$48.84	7.664%	$52.5831	$52.58	$52.60	$52.60
Purchase #5	$124.61	12.447%	$140.1202	$140.12	$140.10	$140.10
Purchase #6	$134.43	8.650%	$146.0582	$146.06	$146.05	$146.10
Purchase #7	$186.90	3.181%	$192.8453	$192.85	$192.85	$192.80
7 purchase totals =	$743.43		$792.2261	$792.23	$792.20	$792.20