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	$88.53	9.270%	$96.7367	$96.74	$96.75	$96.70
Purchase #2	$198.78	5.864%	$210.4365	$210.44	$210.45	$210.40
Purchase #3	$183.84	3.477%	$190.2321	$190.23	$190.25	$190.20
Purchase #4	$54.30	8.774%	$59.0643	$59.06	$59.05	$59.10
Purchase #5	$104.26	5.511%	$110.0058	$110.01	$110.00	$110.00
Purchase #6	$15.96	11.711%	$17.8291	$17.83	$17.85	$17.80
Purchase #7	$145.98	13.223%	$165.2829	$165.28	$165.30	$165.30
7 purchase totals =	$791.65		$849.5874	$849.59	$849.65	$849.50