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	$118.92	7.377%	$127.6927	$127.69	$127.70	$127.70
Purchase #2	$189.44	8.333%	$205.226	$205.23	$205.25	$205.20
Purchase #3	$241.63	4.730%	$253.0591	$253.06	$253.05	$253.10
Purchase #4	$211.35	4.723%	$221.3321	$221.33	$221.35	$221.30
Purchase #5	$196.36	11.723%	$219.3793	$219.38	$219.40	$219.40
Purchase #6	$153.52	5.549%	$162.0388	$162.04	$162.05	$162.00
Purchase #7	$82.53	9.639%	$90.4851	$90.49	$90.50	$90.50
7 purchase totals =	$1,193.75		$1,279.2131	$1,279.22	$1,279.30	$1,279.20