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	$229.93	10.229%	$253.4495	$253.45	$253.45	$253.40
Purchase #2	$32.29	9.752%	$35.4389	$35.44	$35.45	$35.40
Purchase #3	$96.47	4.337%	$100.6539	$100.65	$100.65	$100.70
Purchase #4	$214.57	13.158%	$242.8031	$242.80	$242.80	$242.80
Purchase #5	$250.63	3.165%	$258.5624	$258.56	$258.55	$258.60
Purchase #6	$91.92	3.264%	$94.9203	$94.92	$94.90	$94.90
Purchase #7	$19.39	4.643%	$20.2903	$20.29	$20.30	$20.30
7 purchase totals =	$935.20		$1,006.1184	$1,006.11	$1,006.10	$1,006.10