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	$93.26	3.168%	$96.2145	$96.21	$96.20	$96.20
Purchase #2	$73.73	6.204%	$78.3042	$78.30	$78.30	$78.30
Purchase #3	$80.54	9.112%	$87.8788	$87.88	$87.90	$87.90
Purchase #4	$179.33	8.486%	$194.5479	$194.55	$194.55	$194.50
Purchase #5	$31.87	11.265%	$35.4602	$35.46	$35.45	$35.50
Purchase #6	$250.45	8.850%	$272.6148	$272.61	$272.60	$272.60
Purchase #7	$217.74	9.694%	$238.8477	$238.85	$238.85	$238.80
7 purchase totals =	$926.92		$1,003.8681	$1,003.86	$1,003.85	$1,003.80