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	$31.91	9.813%	$35.0413	$35.04	$35.05	$35.00
Purchase #2	$19.93	3.220%	$20.5717	$20.57	$20.55	$20.60
Purchase #3	$233.50	5.197%	$245.635	$245.64	$245.65	$245.60
Purchase #4	$89.58	10.379%	$98.8775	$98.88	$98.90	$98.90
Purchase #5	$238.81	11.530%	$266.3448	$266.34	$266.35	$266.30
Purchase #6	$85.77	6.459%	$91.3099	$91.31	$91.30	$91.30
Purchase #7	$219.51	11.311%	$244.3388	$244.34	$244.35	$244.30
7 purchase totals =	$919.01		$1,002.1190	$1,002.12	$1,002.15	$1,002.00