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	$92.43	12.784%	$104.2463	$104.25	$104.25	$104.20
Purchase #2	$56.50	4.435%	$59.0058	$59.01	$59.00	$59.00
Purchase #3	$36.99	8.604%	$40.1726	$40.17	$40.15	$40.20
Purchase #4	$130.91	4.498%	$136.7983	$136.80	$136.80	$136.80
Purchase #5	$78.40	11.691%	$87.5657	$87.57	$87.55	$87.60
Purchase #6	$245.28	3.305%	$253.3865	$253.39	$253.40	$253.40
Purchase #7	$89.33	12.662%	$100.641	$100.64	$100.65	$100.60
7 purchase totals =	$729.84		$781.8162	$781.83	$781.80	$781.80