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	$137.82	3.530%	$142.685	$142.69	$142.70	$142.70
Purchase #2	$79.28	4.394%	$82.7636	$82.76	$82.75	$82.80
Purchase #3	$36.96	4.542%	$38.6387	$38.64	$38.65	$38.60
Purchase #4	$57.97	3.341%	$59.9068	$59.91	$59.90	$59.90
Purchase #5	$42.96	13.772%	$48.8765	$48.88	$48.90	$48.90
Purchase #6	$184.75	6.395%	$196.5648	$196.56	$196.55	$196.60
Purchase #7	$119.58	13.499%	$135.7221	$135.72	$135.70	$135.70
7 purchase totals =	$659.32		$705.1575	$705.16	$705.15	$705.20