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	$86.76	5.104%	$91.1882	$91.19	$91.20	$91.20
Purchase #2	$216.34	11.138%	$240.4359	$240.44	$240.45	$240.40
Purchase #3	$36.59	3.201%	$37.7612	$37.76	$37.75	$37.80
Purchase #4	$69.83	11.361%	$77.7634	$77.76	$77.75	$77.80
Purchase #5	$87.34	11.525%	$97.4059	$97.41	$97.40	$97.40
Purchase #6	$64.89	10.269%	$71.5536	$71.55	$71.55	$71.60
Purchase #7	$181.26	6.172%	$192.4474	$192.45	$192.45	$192.40
7 purchase totals =	$743.01		$808.5556	$808.56	$808.55	$808.60