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	$222.86	4.572%	$233.0492	$233.05	$233.05	$233.00
Purchase #2	$151.75	4.424%	$158.4634	$158.46	$158.45	$158.50
Purchase #3	$216.72	13.791%	$246.6079	$246.61	$246.60	$246.60
Purchase #4	$147.44	12.411%	$165.7388	$165.74	$165.75	$165.70
Purchase #5	$229.66	8.215%	$248.5266	$248.53	$248.55	$248.50
Purchase #6	$27.59	13.191%	$31.2294	$31.23	$31.25	$31.20
Purchase #7	$153.83	9.446%	$168.3608	$168.36	$168.35	$168.40
7 purchase totals =	$1,149.85		$1,251.9761	$1,251.98	$1,252.00	$1,251.90