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	$192.27	8.864%	$209.3128	$209.31	$209.30	$209.30
Purchase #2	$84.54	8.752%	$91.9389	$91.94	$91.95	$91.90
Purchase #3	$97.96	11.309%	$109.0383	$109.04	$109.05	$109.00
Purchase #4	$239.76	6.248%	$254.7402	$254.74	$254.75	$254.70
Purchase #5	$233.84	5.159%	$245.9038	$245.90	$245.90	$245.90
Purchase #6	$185.93	5.540%	$196.2305	$196.23	$196.25	$196.20
Purchase #7	$73.59	5.173%	$77.3968	$77.40	$77.40	$77.40
7 purchase totals =	$1,107.89		$1,184.5613	$1,184.56	$1,184.60	$1,184.40