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	$180.70	3.107%	$186.3143	$186.31	$186.30	$186.30
Purchase #2	$141.37	7.510%	$151.9869	$151.99	$152.00	$152.00
Purchase #3	$152.82	8.342%	$165.5682	$165.57	$165.55	$165.60
Purchase #4	$99.53	4.648%	$104.1562	$104.16	$104.15	$104.20
Purchase #5	$158.26	4.798%	$165.8533	$165.85	$165.85	$165.90
Purchase #6	$243.56	4.524%	$254.5787	$254.58	$254.60	$254.60
Purchase #7	$223.86	9.863%	$245.9393	$245.94	$245.95	$245.90
7 purchase totals =	$1,200.10		$1,274.3969	$1,274.40	$1,274.40	$1,274.50