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	$157.63	6.510%	$167.8917	$167.89	$167.90	$167.90
Purchase #2	$48.66	9.630%	$53.346	$53.35	$53.35	$53.30
Purchase #3	$126.71	6.151%	$134.5039	$134.50	$134.50	$134.50
Purchase #4	$149.85	9.839%	$164.5937	$164.59	$164.60	$164.60
Purchase #5	$98.76	11.404%	$110.0226	$110.02	$110.00	$110.00
Purchase #6	$185.94	8.119%	$201.0365	$201.04	$201.05	$201.00
Purchase #7	$175.31	7.310%	$188.1252	$188.13	$188.15	$188.10
7 purchase totals =	$942.86		$1,019.5196	$1,019.52	$1,019.55	$1,019.40