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	$53.25	7.300%	$57.1373	$57.14	$57.15	$57.10
Purchase #2	$44.39	7.468%	$47.705	$47.71	$47.70	$47.70
Purchase #3	$78.87	12.869%	$89.0198	$89.02	$89.00	$89.00
Purchase #4	$69.30	4.372%	$72.3298	$72.33	$72.35	$72.30
Purchase #5	$142.30	4.281%	$148.3919	$148.39	$148.40	$148.40
Purchase #6	$64.97	13.222%	$73.5603	$73.56	$73.55	$73.60
Purchase #7	$211.57	11.410%	$235.7101	$235.71	$235.70	$235.70
7 purchase totals =	$664.65		$723.8542	$723.86	$723.85	$723.80