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	$92.50	11.634%	$103.2615	$103.26	$103.25	$103.30
Purchase #2	$96.51	9.719%	$105.8898	$105.89	$105.90	$105.90
Purchase #3	$187.58	9.443%	$205.2932	$205.29	$205.30	$205.30
Purchase #4	$125.45	6.853%	$134.0471	$134.05	$134.05	$134.00
Purchase #5	$238.61	10.718%	$264.1842	$264.18	$264.20	$264.20
Purchase #6	$162.58	9.561%	$178.1243	$178.12	$178.10	$178.10
Purchase #7	$228.28	8.319%	$247.2706	$247.27	$247.25	$247.30
7 purchase totals =	$1,131.51		$1,238.0707	$1,238.06	$1,238.05	$1,238.10