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	$74.82	3.629%	$77.5352	$77.54	$77.55	$77.50
Purchase #2	$129.92	3.356%	$134.2801	$134.28	$134.30	$134.30
Purchase #3	$99.91	13.717%	$113.6147	$113.61	$113.60	$113.60
Purchase #4	$146.32	6.186%	$155.3714	$155.37	$155.35	$155.40
Purchase #5	$82.68	4.740%	$86.599	$86.60	$86.60	$86.60
Purchase #6	$213.77	4.245%	$222.8445	$222.84	$222.85	$222.80
Purchase #7	$206.92	7.183%	$221.7831	$221.78	$221.80	$221.80
7 purchase totals =	$954.34		$1,012.0280	$1,012.02	$1,012.05	$1,012.00