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	$10.81	4.272%	$11.2718	$11.27	$11.25	$11.30
Purchase #2	$202.40	6.415%	$215.384	$215.38	$215.40	$215.40
Purchase #3	$106.47	4.296%	$111.044	$111.04	$111.05	$111.00
Purchase #4	$221.28	11.515%	$246.7604	$246.76	$246.75	$246.80
Purchase #5	$180.94	12.618%	$203.771	$203.77	$203.75	$203.80
Purchase #6	$154.83	6.651%	$165.1277	$165.13	$165.15	$165.10
Purchase #7	$46.54	8.299%	$50.4024	$50.40	$50.40	$50.40
7 purchase totals =	$923.27		$1,003.7613	$1,003.75	$1,003.75	$1,003.80