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	$175.55	6.137%	$186.3235	$186.32	$186.30	$186.30
Purchase #2	$34.83	7.559%	$37.4628	$37.46	$37.45	$37.50
Purchase #3	$154.40	13.815%	$175.7304	$175.73	$175.75	$175.70
Purchase #4	$55.49	8.191%	$60.0352	$60.04	$60.05	$60.00
Purchase #5	$85.97	4.172%	$89.5567	$89.56	$89.55	$89.60
Purchase #6	$246.40	12.802%	$277.9441	$277.94	$277.95	$277.90
Purchase #7	$236.82	13.572%	$268.9612	$268.96	$268.95	$269.00
7 purchase totals =	$989.46		$1,096.0139	$1,096.01	$1,096.00	$1,096.00