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	$189.41	3.541%	$196.117	$196.12	$196.10	$196.10
Purchase #2	$81.89	9.418%	$89.6024	$89.60	$89.60	$89.60
Purchase #3	$33.50	6.435%	$35.6557	$35.66	$35.65	$35.70
Purchase #4	$44.84	12.280%	$50.3464	$50.35	$50.35	$50.30
Purchase #5	$150.51	4.664%	$157.5298	$157.53	$157.55	$157.50
Purchase #6	$210.57	7.135%	$225.5942	$225.59	$225.60	$225.60
Purchase #7	$194.76	10.281%	$214.7833	$214.78	$214.80	$214.80
7 purchase totals =	$905.48		$969.6288	$969.63	$969.65	$969.60