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	$136.82	3.695%	$141.8755	$141.88	$141.90	$141.90
Purchase #2	$198.25	12.608%	$223.2454	$223.25	$223.25	$223.20
Purchase #3	$52.31	4.679%	$54.7576	$54.76	$54.75	$54.80
Purchase #4	$212.74	3.335%	$219.8349	$219.83	$219.85	$219.80
Purchase #5	$209.71	11.632%	$234.1035	$234.10	$234.10	$234.10
Purchase #6	$145.64	7.270%	$156.228	$156.23	$156.25	$156.20
Purchase #7	$148.88	6.698%	$158.852	$158.85	$158.85	$158.90
7 purchase totals =	$1,104.35		$1,188.8969	$1,188.90	$1,188.95	$1,188.90