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	$89.72	9.260%	$98.0281	$98.03	$98.05	$98.00
Purchase #2	$160.41	13.220%	$181.6162	$181.62	$181.60	$181.60
Purchase #3	$152.99	3.448%	$158.2651	$158.27	$158.25	$158.30
Purchase #4	$195.73	4.253%	$204.0544	$204.05	$204.05	$204.10
Purchase #5	$168.85	4.741%	$176.8552	$176.86	$176.85	$176.90
Purchase #6	$53.30	11.813%	$59.5963	$59.60	$59.60	$59.60
Purchase #7	$205.84	10.238%	$226.9139	$226.91	$226.90	$226.90
7 purchase totals =	$1,026.84		$1,105.3292	$1,105.34	$1,105.30	$1,105.40