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	$98.73	11.127%	$109.7157	$109.72	$109.70	$109.70
Purchase #2	$134.74	11.167%	$149.7864	$149.79	$149.80	$149.80
Purchase #3	$63.88	13.141%	$72.2745	$72.27	$72.25	$72.30
Purchase #4	$149.61	7.561%	$160.922	$160.92	$160.90	$160.90
Purchase #5	$29.83	7.782%	$32.1514	$32.15	$32.15	$32.20
Purchase #6	$152.77	4.150%	$159.11	$159.11	$159.10	$159.10
Purchase #7	$162.42	11.579%	$181.2266	$181.23	$181.25	$181.20
7 purchase totals =	$791.98		$865.1866	$865.19	$865.15	$865.20