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	$223.31	10.331%	$246.3802	$246.38	$246.40	$246.40
Purchase #2	$229.54	3.824%	$238.3176	$238.32	$238.30	$238.30
Purchase #3	$237.92	5.730%	$251.5528	$251.55	$251.55	$251.60
Purchase #4	$58.84	4.355%	$61.4025	$61.40	$61.40	$61.40
Purchase #5	$33.91	10.170%	$37.3586	$37.36	$37.35	$37.40
Purchase #6	$180.25	4.450%	$188.2711	$188.27	$188.25	$188.30
Purchase #7	$117.45	6.228%	$124.7648	$124.76	$124.75	$124.80
7 purchase totals =	$1,081.22		$1,148.0476	$1,148.04	$1,148.00	$1,148.20