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	$190.72	10.809%	$211.3349	$211.33	$211.35	$211.30
Purchase #2	$8.96	7.491%	$9.6312	$9.63	$9.65	$9.60
Purchase #3	$185.49	13.690%	$210.8836	$210.88	$210.90	$210.90
Purchase #4	$72.91	6.461%	$77.6207	$77.62	$77.60	$77.60
Purchase #5	$141.41	13.735%	$160.8327	$160.83	$160.85	$160.80
Purchase #6	$78.74	13.508%	$89.3762	$89.38	$89.40	$89.40
Purchase #7	$104.61	4.538%	$109.3572	$109.36	$109.35	$109.40
7 purchase totals =	$782.84		$869.0365	$869.03	$869.10	$869.00