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	$88.82	3.647%	$92.0593	$92.06	$92.05	$92.10
Purchase #2	$177.65	3.555%	$183.9655	$183.97	$183.95	$184.00
Purchase #3	$90.33	13.728%	$102.7305	$102.73	$102.75	$102.70
Purchase #4	$248.47	3.425%	$256.9801	$256.98	$257.00	$257.00
Purchase #5	$213.52	7.320%	$229.1497	$229.15	$229.15	$229.10
Purchase #6	$53.85	9.829%	$59.1429	$59.14	$59.15	$59.10
Purchase #7	$69.82	3.482%	$72.2511	$72.25	$72.25	$72.30
7 purchase totals =	$942.46		$996.2791	$996.28	$996.30	$996.30