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	$92.61	6.608%	$98.7297	$98.73	$98.75	$98.70
Purchase #2	$172.40	5.177%	$181.3251	$181.33	$181.35	$181.30
Purchase #3	$121.78	5.559%	$128.5498	$128.55	$128.55	$128.50
Purchase #4	$68.46	3.806%	$71.0656	$71.07	$71.05	$71.10
Purchase #5	$50.83	8.782%	$55.2939	$55.29	$55.30	$55.30
Purchase #6	$171.78	7.796%	$185.172	$185.17	$185.15	$185.20
Purchase #7	$196.84	10.196%	$216.9098	$216.91	$216.90	$216.90
7 purchase totals =	$874.70		$937.0459	$937.05	$937.05	$937.00