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	$195.34	13.687%	$222.0762	$222.08	$222.10	$222.10
Purchase #2	$193.75	5.520%	$204.445	$204.45	$204.45	$204.40
Purchase #3	$179.75	3.229%	$185.5541	$185.55	$185.55	$185.60
Purchase #4	$207.84	13.216%	$235.3081	$235.31	$235.30	$235.30
Purchase #5	$16.40	10.218%	$18.0758	$18.08	$18.10	$18.10
Purchase #6	$74.66	10.336%	$82.3769	$82.38	$82.40	$82.40
Purchase #7	$233.31	6.469%	$248.4028	$248.40	$248.40	$248.40
7 purchase totals =	$1,101.05		$1,196.2389	$1,196.25	$1,196.30	$1,196.30