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	$101.58	3.253%	$104.8844	$104.88	$104.90	$104.90
Purchase #2	$160.85	10.858%	$178.3151	$178.32	$178.30	$178.30
Purchase #3	$236.98	6.809%	$253.116	$253.12	$253.10	$253.10
Purchase #4	$158.25	5.819%	$167.4586	$167.46	$167.45	$167.50
Purchase #5	$39.49	7.173%	$42.3226	$42.32	$42.30	$42.30
Purchase #6	$125.73	8.178%	$136.0122	$136.01	$136.00	$136.00
Purchase #7	$185.42	5.608%	$195.8184	$195.82	$195.80	$195.80
7 purchase totals =	$1,008.30		$1,077.9273	$1,077.93	$1,077.85	$1,077.90