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	$205.99	8.403%	$223.2993	$223.30	$223.30	$223.30
Purchase #2	$148.90	13.615%	$169.1727	$169.17	$169.15	$169.20
Purchase #3	$189.41	3.700%	$196.4182	$196.42	$196.40	$196.40
Purchase #4	$250.56	11.213%	$278.6553	$278.66	$278.65	$278.70
Purchase #5	$179.63	12.623%	$202.3047	$202.30	$202.30	$202.30
Purchase #6	$67.54	5.802%	$71.4587	$71.46	$71.45	$71.50
Purchase #7	$51.70	11.226%	$57.5038	$57.50	$57.50	$57.50
7 purchase totals =	$1,093.73		$1,198.8127	$1,198.81	$1,198.75	$1,198.90