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	$207.76	6.398%	$221.0525	$221.05	$221.05	$221.10
Purchase #2	$182.29	6.864%	$194.8024	$194.80	$194.80	$194.80
Purchase #3	$79.96	11.507%	$89.161	$89.16	$89.15	$89.20
Purchase #4	$62.31	6.765%	$66.5253	$66.53	$66.55	$66.50
Purchase #5	$125.59	9.221%	$137.1707	$137.17	$137.15	$137.20
Purchase #6	$51.33	5.815%	$54.3148	$54.31	$54.30	$54.30
Purchase #7	$75.60	9.440%	$82.7366	$82.74	$82.75	$82.70
7 purchase totals =	$784.84		$845.7633	$845.76	$845.75	$845.80