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	$184.47	6.403%	$196.2816	$196.28	$196.30	$196.30
Purchase #2	$95.82	5.700%	$101.2817	$101.28	$101.30	$101.30
Purchase #3	$232.37	5.258%	$244.588	$244.59	$244.60	$244.60
Purchase #4	$159.75	5.365%	$168.3206	$168.32	$168.30	$168.30
Purchase #5	$63.46	12.317%	$71.2764	$71.28	$71.30	$71.30
Purchase #6	$8.80	10.111%	$9.6898	$9.69	$9.70	$9.70
Purchase #7	$51.45	12.543%	$57.9034	$57.90	$57.90	$57.90
7 purchase totals =	$796.12		$849.3415	$849.34	$849.40	$849.40