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	$210.34	5.670%	$222.2663	$222.27	$222.25	$222.30
Purchase #2	$110.66	6.669%	$118.0399	$118.04	$118.05	$118.00
Purchase #3	$71.67	3.814%	$74.4035	$74.40	$74.40	$74.40
Purchase #4	$20.85	5.711%	$22.0407	$22.04	$22.05	$22.00
Purchase #5	$185.69	5.605%	$196.0979	$196.10	$196.10	$196.10
Purchase #6	$64.87	9.629%	$71.1163	$71.12	$71.10	$71.10
Purchase #7	$190.62	13.621%	$216.5844	$216.58	$216.60	$216.60
7 purchase totals =	$854.70		$920.5490	$920.55	$920.55	$920.50