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	$181.92	3.544%	$188.3672	$188.37	$188.35	$188.40
Purchase #2	$228.77	5.222%	$240.7164	$240.72	$240.70	$240.70
Purchase #3	$6.50	11.398%	$7.2409	$7.24	$7.25	$7.20
Purchase #4	$100.55	6.191%	$106.7751	$106.78	$106.80	$106.80
Purchase #5	$91.56	5.277%	$96.3916	$96.39	$96.40	$96.40
Purchase #6	$187.90	4.649%	$196.6355	$196.64	$196.65	$196.60
Purchase #7	$101.39	12.552%	$114.1165	$114.12	$114.10	$114.10
7 purchase totals =	$898.59		$950.2432	$950.26	$950.25	$950.20