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	$92.92	7.111%	$99.5275	$99.53	$99.55	$99.50
Purchase #2	$87.83	4.590%	$91.8614	$91.86	$91.85	$91.90
Purchase #3	$225.58	6.693%	$240.6781	$240.68	$240.70	$240.70
Purchase #4	$232.83	13.498%	$264.2574	$264.26	$264.25	$264.30
Purchase #5	$61.76	5.632%	$65.2383	$65.24	$65.25	$65.20
Purchase #6	$243.27	13.398%	$275.8633	$275.86	$275.85	$275.90
Purchase #7	$140.79	7.155%	$150.8635	$150.86	$150.85	$150.90
7 purchase totals =	$1,084.98		$1,188.2895	$1,188.29	$1,188.30	$1,188.40