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	$139.67	5.279%	$147.0432	$147.04	$147.05	$147.00
Purchase #2	$142.38	5.471%	$150.1696	$150.17	$150.15	$150.20
Purchase #3	$182.46	4.638%	$190.9225	$190.92	$190.90	$190.90
Purchase #4	$9.49	13.418%	$10.7634	$10.76	$10.75	$10.80
Purchase #5	$31.59	4.785%	$33.1016	$33.10	$33.10	$33.10
Purchase #6	$160.63	4.675%	$168.1395	$168.14	$168.15	$168.10
Purchase #7	$115.43	12.279%	$129.6036	$129.60	$129.60	$129.60
7 purchase totals =	$781.65		$829.7434	$829.73	$829.70	$829.70