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	$147.79	9.864%	$162.368	$162.37	$162.35	$162.40
Purchase #2	$145.97	3.639%	$151.2818	$151.28	$151.30	$151.30
Purchase #3	$57.32	4.529%	$59.916	$59.92	$59.90	$59.90
Purchase #4	$53.67	11.120%	$59.6381	$59.64	$59.65	$59.60
Purchase #5	$70.28	3.434%	$72.6934	$72.69	$72.70	$72.70
Purchase #6	$207.70	7.406%	$223.0823	$223.08	$223.10	$223.10
Purchase #7	$45.82	10.530%	$50.6448	$50.64	$50.65	$50.60
7 purchase totals =	$728.55		$779.6244	$779.62	$779.65	$779.60