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	$105.48	5.266%	$111.0346	$111.03	$111.05	$111.00
Purchase #2	$106.37	3.665%	$110.2685	$110.27	$110.25	$110.30
Purchase #3	$60.52	8.860%	$65.8821	$65.88	$65.90	$65.90
Purchase #4	$82.43	4.224%	$85.9118	$85.91	$85.90	$85.90
Purchase #5	$6.35	12.561%	$7.1476	$7.15	$7.15	$7.10
Purchase #6	$218.97	6.482%	$233.1636	$233.16	$233.15	$233.20
Purchase #7	$153.82	9.111%	$167.8345	$167.83	$167.85	$167.80
7 purchase totals =	$733.94		$781.2427	$781.23	$781.25	$781.20