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	$55.67	7.274%	$59.7194	$59.72	$59.70	$59.70
Purchase #2	$173.99	10.318%	$191.9423	$191.94	$191.95	$191.90
Purchase #3	$67.62	7.152%	$72.4562	$72.46	$72.45	$72.50
Purchase #4	$138.53	12.648%	$156.0513	$156.05	$156.05	$156.10
Purchase #5	$196.68	13.506%	$223.2436	$223.24	$223.25	$223.20
Purchase #6	$233.30	6.203%	$247.7716	$247.77	$247.75	$247.80
Purchase #7	$197.56	12.644%	$222.5395	$222.54	$222.55	$222.50
7 purchase totals =	$1,063.35		$1,173.7239	$1,173.72	$1,173.70	$1,173.70