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	$89.51	3.265%	$92.4325	$92.43	$92.45	$92.40
Purchase #2	$129.27	11.805%	$144.5303	$144.53	$144.55	$144.50
Purchase #3	$67.33	11.520%	$75.0864	$75.09	$75.10	$75.10
Purchase #4	$152.32	3.417%	$157.5248	$157.52	$157.50	$157.50
Purchase #5	$210.49	12.279%	$236.3361	$236.34	$236.35	$236.30
Purchase #6	$127.74	11.742%	$142.7392	$142.74	$142.75	$142.70
Purchase #7	$154.40	10.817%	$171.1014	$171.10	$171.10	$171.10
7 purchase totals =	$931.06		$1,019.7507	$1,019.75	$1,019.80	$1,019.60