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	$148.82	5.871%	$157.5572	$157.56	$157.55	$157.60
Purchase #2	$123.30	5.400%	$129.9582	$129.96	$129.95	$130.00
Purchase #3	$81.85	10.495%	$90.4402	$90.44	$90.45	$90.40
Purchase #4	$210.97	5.220%	$221.9826	$221.98	$222.00	$222.00
Purchase #5	$48.89	10.680%	$54.1115	$54.11	$54.10	$54.10
Purchase #6	$18.76	4.192%	$19.5464	$19.55	$19.55	$19.50
Purchase #7	$182.27	10.197%	$200.8561	$200.86	$200.85	$200.90
7 purchase totals =	$814.86		$874.4522	$874.46	$874.45	$874.50