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	$175.98	12.816%	$198.5336	$198.53	$198.55	$198.50
Purchase #2	$99.53	3.484%	$102.9976	$103.00	$103.00	$103.00
Purchase #3	$54.99	7.533%	$59.1324	$59.13	$59.15	$59.10
Purchase #4	$229.98	4.501%	$240.3314	$240.33	$240.35	$240.30
Purchase #5	$177.75	4.570%	$185.8732	$185.87	$185.85	$185.90
Purchase #6	$244.69	13.746%	$278.3251	$278.33	$278.35	$278.30
Purchase #7	$240.63	3.611%	$249.3191	$249.32	$249.30	$249.30
7 purchase totals =	$1,223.55		$1,314.5124	$1,314.51	$1,314.55	$1,314.40