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	$196.99	9.454%	$215.6134	$215.61	$215.60	$215.60
Purchase #2	$175.70	12.184%	$197.1073	$197.11	$197.10	$197.10
Purchase #3	$211.83	7.827%	$228.4099	$228.41	$228.40	$228.40
Purchase #4	$35.82	3.648%	$37.1267	$37.13	$37.15	$37.10
Purchase #5	$47.27	12.134%	$53.0057	$53.01	$53.00	$53.00
Purchase #6	$37.75	9.758%	$41.4336	$41.43	$41.45	$41.40
Purchase #7	$244.78	13.760%	$278.4617	$278.46	$278.45	$278.50
7 purchase totals =	$950.14		$1,051.1583	$1,051.16	$1,051.15	$1,051.10