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	$187.82	4.658%	$196.5687	$196.57	$196.55	$196.60
Purchase #2	$151.48	13.690%	$172.2176	$172.22	$172.20	$172.20
Purchase #3	$173.50	12.718%	$195.5657	$195.57	$195.55	$195.60
Purchase #4	$178.35	7.250%	$191.2804	$191.28	$191.30	$191.30
Purchase #5	$25.44	12.757%	$28.6854	$28.69	$28.70	$28.70
Purchase #6	$214.62	11.572%	$239.4558	$239.46	$239.45	$239.50
Purchase #7	$139.33	13.402%	$158.003	$158.00	$158.00	$158.00
7 purchase totals =	$1,070.54		$1,181.7766	$1,181.79	$1,181.75	$1,181.90