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	$44.40	7.860%	$47.8898	$47.89	$47.90	$47.90
Purchase #2	$34.74	8.502%	$37.6936	$37.69	$37.70	$37.70
Purchase #3	$221.69	7.431%	$238.1638	$238.16	$238.15	$238.20
Purchase #4	$206.49	8.287%	$223.6018	$223.60	$223.60	$223.60
Purchase #5	$61.56	9.842%	$67.6187	$67.62	$67.60	$67.60
Purchase #6	$44.61	11.810%	$49.8784	$49.88	$49.90	$49.90
Purchase #7	$84.99	13.843%	$96.7552	$96.76	$96.75	$96.80
7 purchase totals =	$698.48		$761.6013	$761.60	$761.60	$761.70