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	$230.45	7.331%	$247.3443	$247.34	$247.35	$247.30
Purchase #2	$57.82	4.581%	$60.4687	$60.47	$60.45	$60.50
Purchase #3	$72.86	13.231%	$82.5001	$82.50	$82.50	$82.50
Purchase #4	$204.54	6.765%	$218.3771	$218.38	$218.40	$218.40
Purchase #5	$191.32	7.553%	$205.7704	$205.77	$205.75	$205.80
Purchase #6	$78.52	10.108%	$86.4568	$86.46	$86.45	$86.50
Purchase #7	$96.72	13.503%	$109.7801	$109.78	$109.80	$109.80
7 purchase totals =	$932.23		$1,010.6975	$1,010.70	$1,010.70	$1,010.80