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	$212.57	5.405%	$224.0594	$224.06	$224.05	$224.10
Purchase #2	$53.56	10.395%	$59.1276	$59.13	$59.15	$59.10
Purchase #3	$94.36	13.334%	$106.942	$106.94	$106.95	$106.90
Purchase #4	$54.32	9.782%	$59.6336	$59.63	$59.65	$59.60
Purchase #5	$146.95	3.132%	$151.5525	$151.55	$151.55	$151.60
Purchase #6	$28.67	7.677%	$30.871	$30.87	$30.85	$30.90
Purchase #7	$138.91	7.148%	$148.8393	$148.84	$148.85	$148.80
7 purchase totals =	$729.34		$781.0254	$781.02	$781.05	$781.00