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	$191.64	4.844%	$200.923	$200.92	$200.90	$200.90
Purchase #2	$202.50	7.636%	$217.9629	$217.96	$217.95	$218.00
Purchase #3	$147.76	11.721%	$165.0789	$165.08	$165.10	$165.10
Purchase #4	$46.33	8.608%	$50.3181	$50.32	$50.30	$50.30
Purchase #5	$227.86	9.851%	$250.3065	$250.31	$250.30	$250.30
Purchase #6	$199.64	11.123%	$221.846	$221.85	$221.85	$221.80
Purchase #7	$59.27	10.707%	$65.616	$65.62	$65.60	$65.60
7 purchase totals =	$1,075.00		$1,172.0514	$1,172.06	$1,172.00	$1,172.00