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	$158.73	10.120%	$174.7935	$174.79	$174.80	$174.80
Purchase #2	$228.86	8.664%	$248.6884	$248.69	$248.70	$248.70
Purchase #3	$102.55	3.144%	$105.7742	$105.77	$105.75	$105.80
Purchase #4	$39.29	6.840%	$41.9774	$41.98	$42.00	$42.00
Purchase #5	$167.48	9.323%	$183.0942	$183.09	$183.10	$183.10
Purchase #6	$69.98	11.671%	$78.1474	$78.15	$78.15	$78.10
Purchase #7	$105.50	4.169%	$109.8983	$109.90	$109.90	$109.90
7 purchase totals =	$872.39		$942.3734	$942.37	$942.40	$942.40