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	$153.59	10.296%	$169.4036	$169.40	$169.40	$169.40
Purchase #2	$26.35	6.328%	$28.0174	$28.02	$28.00	$28.00
Purchase #3	$147.25	7.405%	$158.1539	$158.15	$158.15	$158.20
Purchase #4	$227.62	4.514%	$237.8948	$237.89	$237.90	$237.90
Purchase #5	$87.67	7.833%	$94.5372	$94.54	$94.55	$94.50
Purchase #6	$55.91	4.379%	$58.3583	$58.36	$58.35	$58.40
Purchase #7	$182.55	7.667%	$196.5461	$196.55	$196.55	$196.50
7 purchase totals =	$880.94		$942.9113	$942.91	$942.90	$942.90