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	$235.89	6.790%	$251.9069	$251.91	$251.90	$251.90
Purchase #2	$42.89	13.873%	$48.8401	$48.84	$48.85	$48.80
Purchase #3	$37.76	6.418%	$40.1834	$40.18	$40.20	$40.20
Purchase #4	$78.62	3.487%	$81.3615	$81.36	$81.35	$81.40
Purchase #5	$247.52	8.102%	$267.5741	$267.57	$267.55	$267.60
Purchase #6	$228.65	4.222%	$238.3036	$238.30	$238.30	$238.30
Purchase #7	$67.44	8.688%	$73.2992	$73.30	$73.30	$73.30
7 purchase totals =	$938.77		$1,001.4688	$1,001.46	$1,001.45	$1,001.50