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	$35.25	6.467%	$37.5296	$37.53	$37.55	$37.50
Purchase #2	$147.85	12.394%	$166.1745	$166.17	$166.15	$166.20
Purchase #3	$36.85	7.798%	$39.7236	$39.72	$39.70	$39.70
Purchase #4	$157.30	6.791%	$167.9822	$167.98	$168.00	$168.00
Purchase #5	$150.30	3.781%	$155.9828	$155.98	$156.00	$156.00
Purchase #6	$245.93	9.432%	$269.1261	$269.13	$269.15	$269.10
Purchase #7	$221.84	12.755%	$250.1357	$250.14	$250.15	$250.10
7 purchase totals =	$995.32		$1,086.6545	$1,086.65	$1,086.70	$1,086.60