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	$51.26	4.586%	$53.6108	$53.61	$53.60	$53.60
Purchase #2	$98.30	12.606%	$110.6917	$110.69	$110.70	$110.70
Purchase #3	$78.52	4.720%	$82.2261	$82.23	$82.25	$82.20
Purchase #4	$45.68	5.797%	$48.3281	$48.33	$48.35	$48.30
Purchase #5	$147.69	6.103%	$156.7035	$156.70	$156.70	$156.70
Purchase #6	$86.68	4.547%	$90.6213	$90.62	$90.60	$90.60
Purchase #7	$181.62	12.445%	$204.2226	$204.22	$204.20	$204.20
7 purchase totals =	$689.75		$746.4041	$746.40	$746.40	$746.30