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	$92.77	10.271%	$102.2984	$102.30	$102.30	$102.30
Purchase #2	$50.55	6.104%	$53.6356	$53.64	$53.65	$53.60
Purchase #3	$35.72	3.771%	$37.067	$37.07	$37.05	$37.10
Purchase #4	$17.88	9.368%	$19.555	$19.56	$19.55	$19.60
Purchase #5	$26.65	5.308%	$28.0646	$28.06	$28.05	$28.10
Purchase #6	$30.59	4.813%	$32.0623	$32.06	$32.05	$32.10
Purchase #7	$76.37	13.705%	$86.8365	$86.84	$86.85	$86.80
7 purchase totals =	$330.53		$359.5194	$359.53	$359.50	$359.60