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	$111.59	11.206%	$124.0948	$124.09	$124.10	$124.10
Purchase #2	$41.95	11.241%	$46.6656	$46.67	$46.65	$46.70
Purchase #3	$222.86	8.498%	$241.7986	$241.80	$241.80	$241.80
Purchase #4	$205.72	3.121%	$212.1405	$212.14	$212.15	$212.10
Purchase #5	$127.47	11.272%	$141.8384	$141.84	$141.85	$141.80
Purchase #6	$116.66	7.340%	$125.2228	$125.22	$125.20	$125.20
Purchase #7	$115.40	10.568%	$127.5955	$127.60	$127.60	$127.60
7 purchase totals =	$941.65		$1,019.3562	$1,019.36	$1,019.35	$1,019.30