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	$188.52	11.380%	$209.9736	$209.97	$209.95	$210.00
Purchase #2	$97.33	7.322%	$104.4565	$104.46	$104.45	$104.50
Purchase #3	$41.28	13.231%	$46.7418	$46.74	$46.75	$46.70
Purchase #4	$160.46	6.704%	$171.2172	$171.22	$171.20	$171.20
Purchase #5	$128.89	3.410%	$133.2851	$133.29	$133.30	$133.30
Purchase #6	$207.69	3.546%	$215.0547	$215.05	$215.05	$215.10
Purchase #7	$242.37	11.644%	$270.5916	$270.59	$270.60	$270.60
7 purchase totals =	$1,066.54		$1,151.3205	$1,151.32	$1,151.30	$1,151.40