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	$170.29	8.321%	$184.4598	$184.46	$184.45	$184.50
Purchase #2	$191.67	3.435%	$198.2539	$198.25	$198.25	$198.30
Purchase #3	$150.25	6.699%	$160.3152	$160.32	$160.30	$160.30
Purchase #4	$32.86	13.507%	$37.2984	$37.30	$37.30	$37.30
Purchase #5	$69.85	3.298%	$72.1537	$72.15	$72.15	$72.20
Purchase #6	$54.34	10.860%	$60.2413	$60.24	$60.25	$60.20
Purchase #7	$58.56	4.641%	$61.2778	$61.28	$61.30	$61.30
7 purchase totals =	$727.82		$774.0001	$774.00	$774.00	$774.10