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	$82.49	11.716%	$92.1545	$92.15	$92.15	$92.20
Purchase #2	$181.87	12.414%	$204.4473	$204.45	$204.45	$204.40
Purchase #3	$51.88	3.740%	$53.8203	$53.82	$53.80	$53.80
Purchase #4	$83.90	9.207%	$91.6247	$91.62	$91.60	$91.60
Purchase #5	$131.76	13.435%	$149.462	$149.46	$149.45	$149.50
Purchase #6	$171.30	12.354%	$192.4624	$192.46	$192.45	$192.50
Purchase #7	$96.37	9.339%	$105.37	$105.37	$105.35	$105.40
7 purchase totals =	$799.57		$889.3412	$889.33	$889.25	$889.40