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	$47.54	6.245%	$50.5089	$50.51	$50.50	$50.50
Purchase #2	$217.55	7.548%	$233.9707	$233.97	$233.95	$234.00
Purchase #3	$33.52	5.376%	$35.322	$35.32	$35.30	$35.30
Purchase #4	$89.50	12.267%	$100.479	$100.48	$100.50	$100.50
Purchase #5	$181.30	6.623%	$193.3075	$193.31	$193.30	$193.30
Purchase #6	$209.76	10.286%	$231.3359	$231.34	$231.35	$231.30
Purchase #7	$178.37	3.388%	$184.4132	$184.41	$184.40	$184.40
7 purchase totals =	$957.54		$1,029.3372	$1,029.34	$1,029.30	$1,029.30