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	$191.37	13.119%	$216.4758	$216.48	$216.50	$216.50
Purchase #2	$146.50	7.430%	$157.385	$157.39	$157.40	$157.40
Purchase #3	$147.53	5.106%	$155.0629	$155.06	$155.05	$155.10
Purchase #4	$103.56	5.526%	$109.2827	$109.28	$109.30	$109.30
Purchase #5	$88.26	9.497%	$96.6421	$96.64	$96.65	$96.60
Purchase #6	$153.36	13.608%	$174.2292	$174.23	$174.25	$174.20
Purchase #7	$154.93	6.124%	$164.4179	$164.42	$164.40	$164.40
7 purchase totals =	$985.51		$1,073.4956	$1,073.50	$1,073.55	$1,073.50