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	$179.58	10.695%	$198.7861	$198.79	$198.80	$198.80
Purchase #2	$148.45	9.746%	$162.9179	$162.92	$162.90	$162.90
Purchase #3	$31.67	6.654%	$33.7773	$33.78	$33.80	$33.80
Purchase #4	$167.53	12.854%	$189.0643	$189.06	$189.05	$189.10
Purchase #5	$41.41	10.643%	$45.8173	$45.82	$45.80	$45.80
Purchase #6	$96.73	7.321%	$103.8116	$103.81	$103.80	$103.80
Purchase #7	$170.42	11.383%	$189.8189	$189.82	$189.80	$189.80
7 purchase totals =	$835.79		$923.9934	$924.00	$923.95	$924.00