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	$168.46	6.337%	$179.1353	$179.14	$179.15	$179.10
Purchase #2	$233.60	7.111%	$250.2113	$250.21	$250.20	$250.20
Purchase #3	$36.84	12.234%	$41.347	$41.35	$41.35	$41.30
Purchase #4	$170.37	11.108%	$189.2947	$189.29	$189.30	$189.30
Purchase #5	$91.89	6.689%	$98.0365	$98.04	$98.05	$98.00
Purchase #6	$138.91	6.171%	$147.4821	$147.48	$147.50	$147.50
Purchase #7	$158.42	7.229%	$169.8722	$169.87	$169.85	$169.90
7 purchase totals =	$998.49		$1,075.3791	$1,075.38	$1,075.40	$1,075.30