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	$164.95	12.314%	$185.2619	$185.26	$185.25	$185.30
Purchase #2	$233.63	13.412%	$264.9645	$264.96	$264.95	$265.00
Purchase #3	$137.53	13.112%	$155.5629	$155.56	$155.55	$155.60
Purchase #4	$92.35	11.585%	$103.0487	$103.05	$103.05	$103.00
Purchase #5	$176.82	6.473%	$188.2656	$188.27	$188.25	$188.30
Purchase #6	$89.27	6.795%	$95.3359	$95.34	$95.35	$95.30
Purchase #7	$221.75	9.284%	$242.3373	$242.34	$242.35	$242.30
7 purchase totals =	$1,116.30		$1,234.7768	$1,234.78	$1,234.75	$1,234.80