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	$105.69	6.295%	$112.3432	$112.34	$112.35	$112.30
Purchase #2	$97.98	9.702%	$107.486	$107.49	$107.50	$107.50
Purchase #3	$89.63	4.744%	$93.882	$93.88	$93.90	$93.90
Purchase #4	$227.49	7.485%	$244.5176	$244.52	$244.50	$244.50
Purchase #5	$103.35	6.284%	$109.8445	$109.84	$109.85	$109.80
Purchase #6	$106.61	4.406%	$111.3072	$111.31	$111.30	$111.30
Purchase #7	$222.73	8.839%	$242.4171	$242.42	$242.40	$242.40
7 purchase totals =	$953.48		$1,021.7976	$1,021.80	$1,021.80	$1,021.70