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	$199.55	5.197%	$209.9206	$209.92	$209.90	$209.90
Purchase #2	$53.66	5.700%	$56.7186	$56.72	$56.70	$56.70
Purchase #3	$98.69	4.701%	$103.3294	$103.33	$103.35	$103.30
Purchase #4	$28.39	13.250%	$32.1517	$32.15	$32.15	$32.20
Purchase #5	$112.39	6.118%	$119.266	$119.27	$119.25	$119.30
Purchase #6	$143.29	12.332%	$160.9605	$160.96	$160.95	$161.00
Purchase #7	$130.77	11.400%	$145.6778	$145.68	$145.70	$145.70
7 purchase totals =	$766.74		$828.0246	$828.03	$828.00	$828.10