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	$47.77	10.741%	$52.901	$52.90	$52.90	$52.90
Purchase #2	$79.78	4.421%	$83.3071	$83.31	$83.30	$83.30
Purchase #3	$41.49	9.613%	$45.4784	$45.48	$45.50	$45.50
Purchase #4	$218.96	7.542%	$235.474	$235.47	$235.45	$235.50
Purchase #5	$154.37	6.467%	$164.3531	$164.35	$164.35	$164.40
Purchase #6	$16.27	12.663%	$18.3303	$18.33	$18.35	$18.30
Purchase #7	$94.31	12.624%	$106.2157	$106.22	$106.20	$106.20
7 purchase totals =	$652.95		$706.0596	$706.06	$706.05	$706.10