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	$104.36	5.140%	$109.7241	$109.72	$109.70	$109.70
Purchase #2	$244.52	6.333%	$260.0055	$260.01	$260.00	$260.00
Purchase #3	$202.38	9.355%	$221.3126	$221.31	$221.30	$221.30
Purchase #4	$43.27	6.122%	$45.919	$45.92	$45.90	$45.90
Purchase #5	$219.67	10.498%	$242.731	$242.73	$242.75	$242.70
Purchase #6	$101.88	8.362%	$110.3992	$110.40	$110.40	$110.40
Purchase #7	$89.34	13.140%	$101.0793	$101.08	$101.10	$101.10
7 purchase totals =	$1,005.42		$1,091.1707	$1,091.17	$1,091.15	$1,091.10