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	$24.42	6.193%	$25.9323	$25.93	$25.95	$25.90
Purchase #2	$200.53	13.765%	$228.133	$228.13	$228.15	$228.10
Purchase #3	$51.34	7.691%	$55.2886	$55.29	$55.30	$55.30
Purchase #4	$224.90	11.346%	$250.4172	$250.42	$250.40	$250.40
Purchase #5	$149.91	7.250%	$160.7785	$160.78	$160.80	$160.80
Purchase #6	$68.78	5.394%	$72.49	$72.49	$72.50	$72.50
Purchase #7	$229.32	11.319%	$255.2767	$255.28	$255.30	$255.30
7 purchase totals =	$949.20		$1,048.3163	$1,048.32	$1,048.40	$1,048.30