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	$202.73	3.285%	$209.3897	$209.39	$209.40	$209.40
Purchase #2	$163.73	3.286%	$169.1102	$169.11	$169.10	$169.10
Purchase #3	$185.47	5.782%	$196.1939	$196.19	$196.20	$196.20
Purchase #4	$245.60	7.699%	$264.5087	$264.51	$264.50	$264.50
Purchase #5	$42.25	7.769%	$45.5324	$45.53	$45.55	$45.50
Purchase #6	$49.84	9.735%	$54.6919	$54.69	$54.70	$54.70
Purchase #7	$129.72	6.524%	$138.1829	$138.18	$138.20	$138.20
7 purchase totals =	$1,019.34		$1,077.6097	$1,077.60	$1,077.65	$1,077.60