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	$183.52	3.478%	$189.9028	$189.90	$189.90	$189.90
Purchase #2	$232.31	4.752%	$243.3494	$243.35	$243.35	$243.30
Purchase #3	$106.34	9.764%	$116.723	$116.72	$116.70	$116.70
Purchase #4	$36.61	3.102%	$37.7456	$37.75	$37.75	$37.70
Purchase #5	$115.35	10.831%	$127.8436	$127.84	$127.85	$127.80
Purchase #6	$227.97	13.784%	$259.3934	$259.39	$259.40	$259.40
Purchase #7	$158.46	8.585%	$172.0638	$172.06	$172.05	$172.10
7 purchase totals =	$1,060.56		$1,147.0216	$1,147.01	$1,147.00	$1,146.90