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	$175.52	3.181%	$181.1033	$181.10	$181.10	$181.10
Purchase #2	$182.51	6.740%	$194.8112	$194.81	$194.80	$194.80
Purchase #3	$180.60	12.278%	$202.7741	$202.77	$202.75	$202.80
Purchase #4	$98.89	7.443%	$106.2504	$106.25	$106.25	$106.30
Purchase #5	$52.79	12.679%	$59.4832	$59.48	$59.50	$59.50
Purchase #6	$110.37	12.696%	$124.3826	$124.38	$124.40	$124.40
Purchase #7	$165.83	9.771%	$182.0332	$182.03	$182.05	$182.00
7 purchase totals =	$966.51		$1,050.8380	$1,050.82	$1,050.85	$1,050.90