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	$44.48	6.159%	$47.2195	$47.22	$47.20	$47.20
Purchase #2	$55.85	12.640%	$62.9094	$62.91	$62.90	$62.90
Purchase #3	$97.64	11.694%	$109.058	$109.06	$109.05	$109.10
Purchase #4	$62.34	3.612%	$64.5917	$64.59	$64.60	$64.60
Purchase #5	$106.42	4.807%	$111.5356	$111.54	$111.55	$111.50
Purchase #6	$96.56	4.327%	$100.7382	$100.74	$100.75	$100.70
Purchase #7	$245.75	4.377%	$256.5065	$256.51	$256.50	$256.50
7 purchase totals =	$709.04		$752.5589	$752.57	$752.55	$752.50