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	$17.36	5.759%	$18.3598	$18.36	$18.35	$18.40
Purchase #2	$207.37	7.207%	$222.3152	$222.32	$222.30	$222.30
Purchase #3	$84.26	11.404%	$93.869	$93.87	$93.85	$93.90
Purchase #4	$209.71	6.632%	$223.618	$223.62	$223.60	$223.60
Purchase #5	$132.92	5.171%	$139.7933	$139.79	$139.80	$139.80
Purchase #6	$162.96	4.385%	$170.1058	$170.11	$170.10	$170.10
Purchase #7	$228.62	6.328%	$243.0871	$243.09	$243.10	$243.10
7 purchase totals =	$1,043.20		$1,111.1482	$1,111.16	$1,111.10	$1,111.20