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	$71.94	6.104%	$76.3312	$76.33	$76.35	$76.30
Purchase #2	$99.99	12.281%	$112.2698	$112.27	$112.25	$112.30
Purchase #3	$166.85	5.641%	$176.262	$176.26	$176.25	$176.30
Purchase #4	$51.73	13.846%	$58.8925	$58.89	$58.90	$58.90
Purchase #5	$213.71	13.393%	$242.3322	$242.33	$242.35	$242.30
Purchase #6	$93.61	3.531%	$96.9154	$96.92	$96.90	$96.90
Purchase #7	$176.83	4.761%	$185.2489	$185.25	$185.25	$185.20
7 purchase totals =	$874.66		$948.2520	$948.25	$948.25	$948.20