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	$97.65	8.243%	$105.6993	$105.70	$105.70	$105.70
Purchase #2	$154.83	11.262%	$172.267	$172.27	$172.25	$172.30
Purchase #3	$117.83	7.199%	$126.3126	$126.31	$126.30	$126.30
Purchase #4	$160.44	6.453%	$170.7932	$170.79	$170.80	$170.80
Purchase #5	$211.26	6.286%	$224.5398	$224.54	$224.55	$224.50
Purchase #6	$115.94	6.396%	$123.3555	$123.36	$123.35	$123.40
Purchase #7	$223.60	8.801%	$243.279	$243.28	$243.30	$243.30
7 purchase totals =	$1,081.55		$1,166.2464	$1,166.25	$1,166.25	$1,166.30