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	$104.86	6.143%	$111.3015	$111.30	$111.30	$111.30
Purchase #2	$206.29	4.249%	$215.0553	$215.06	$215.05	$215.10
Purchase #3	$148.81	11.846%	$166.438	$166.44	$166.45	$166.40
Purchase #4	$68.30	4.443%	$71.3346	$71.33	$71.35	$71.30
Purchase #5	$187.61	11.486%	$209.1589	$209.16	$209.15	$209.20
Purchase #6	$20.30	5.289%	$21.3737	$21.37	$21.35	$21.40
Purchase #7	$158.69	4.206%	$165.3645	$165.36	$165.35	$165.40
7 purchase totals =	$894.86		$960.0265	$960.02	$960.00	$960.10