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	$113.27	4.125%	$117.9424	$117.94	$117.95	$117.90
Purchase #2	$98.40	6.698%	$104.9908	$104.99	$105.00	$105.00
Purchase #3	$247.99	6.625%	$264.4193	$264.42	$264.40	$264.40
Purchase #4	$97.71	5.839%	$103.4153	$103.42	$103.40	$103.40
Purchase #5	$224.34	9.594%	$245.8632	$245.86	$245.85	$245.90
Purchase #6	$81.54	4.712%	$85.3822	$85.38	$85.40	$85.40
Purchase #7	$152.45	6.300%	$162.0544	$162.05	$162.05	$162.10
7 purchase totals =	$1,015.70		$1,084.0676	$1,084.06	$1,084.05	$1,084.10