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	$171.83	11.731%	$191.9874	$191.99	$192.00	$192.00
Purchase #2	$85.61	6.479%	$91.1567	$91.16	$91.15	$91.20
Purchase #3	$79.79	12.541%	$89.7965	$89.80	$89.80	$89.80
Purchase #4	$135.66	3.846%	$140.8775	$140.88	$140.90	$140.90
Purchase #5	$167.49	10.838%	$185.6426	$185.64	$185.65	$185.60
Purchase #6	$9.63	5.125%	$10.1235	$10.12	$10.10	$10.10
Purchase #7	$72.39	13.819%	$82.3936	$82.39	$82.40	$82.40
7 purchase totals =	$722.40		$791.9778	$791.98	$792.00	$792.00