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	$148.96	13.624%	$169.2543	$169.25	$169.25	$169.30
Purchase #2	$205.44	11.306%	$228.667	$228.67	$228.65	$228.70
Purchase #3	$75.33	4.565%	$78.7688	$78.77	$78.75	$78.80
Purchase #4	$55.53	6.586%	$59.1872	$59.19	$59.20	$59.20
Purchase #5	$31.80	6.156%	$33.7576	$33.76	$33.75	$33.80
Purchase #6	$85.65	12.374%	$96.2483	$96.25	$96.25	$96.20
Purchase #7	$237.40	7.237%	$254.5806	$254.58	$254.60	$254.60
7 purchase totals =	$840.11		$920.4638	$920.47	$920.45	$920.60